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200
Fig. 10.6 Rinne test
S. Celik et al.
Gelle Test
It is also a special test performed with a tuning fork. The purpose of the test is to
determine whether the stapes is mobile or xed. It is especially helpful in diagnosing otosclerosis. In a healthy person, when a vibrating tuning fork is placed on the
mastoid and positive air pressure is applied to the EAC with a pneumatic otoscope,
the tuning fork sound decreases or disappears as the base of the stapes is pushed
toward the oval window membrane. When negative pressure is applied by suction,
the patient will report hearing the sound again. In cases where the stapes is xed,
there would be no change in hearing during this test [24–26].
The tests used for further evaluation and audiometric assessment of patients with
hearing and balance problems are described in detail in the appropriate sections.
10.3 Conclusion
Although technology has advanced, basic otologic examination methods are still
important today and help us diagnose many diseases. For this reason, it is very
important to know and apply basic otologic examination tests and patient history taking.
10 Otologic History Taking andBasic Examination Techniques
201
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3. Harrison E, Cronin M.Otalgia. Aust Fam Physician. 2016;45(7):493–7.
4. Earwood JS, Rogers TS, Rathjen NA.Ear pain: diagnosing common and uncommon causes.
Am Fam Physician. 2018;97(1):20–7.
5. Öcal FCA, Yılmaz YF, Peng KA.Otorrhea: pathogenesis, diagnosis, and treatment. Pediatric
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6. Golpanian RS, Smith P, Yosipovitch G.Itch in organs beyond the skin. Curr Allergy Asthma
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8. Jarach CM, Lugo A, Scala M, etal. Global prevalence and incidence of tinnitus: a systematic review and meta-analysis [published correction appears in JAMA Neurol.
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complaints in a pediatric examination. Int Arch Otorhinolaryngol. 2019;23(1):36–40. https://
doi.org/10.1055/s- 0038- 1667007.
10. Pichichero ME, Poole MD.Comparison of performance by otolaryngologists, pediatricians,
and general practioners on an otoendoscopic diagnostic video examination. Int J Pediatr
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11. Lieberthal AS, Carroll AE, Chonmaitree T, etal. The diagnosis and management of acute otitis
media. Pediatrics. 2013;131(03):e964–99.
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Publishing; 2023.
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14. Sargent SJ, Frank LA, Buchanan BR, Donnell RL, Morandi F. Otoscopic, cytological, and
microbiological examination of the equine external ear canal. Vet Dermatol. 2006;17(3):175–81.
https://doi.org/10.1111/j.1365- 3164.2006.00515.x.
15. Won J, Monroy GL, Huang PC, etal. Pneumatic low-coherence interferometry otoscope
to quantify tympanic membrane mobility and middle ear pressure. Biomed Opt Express.
2018;9(2):397–409. https://doi.org/10.1364/BOE.9.000397.
16. Ridge SE, Shetty KR, Lee DJ. Current trends and applications in endoscopy for otology
and neurotology. World J Otorhinolaryngol Head Neck Surg. 2021;7(2):101–8. https://doi.
org/10.1016/j.wjorl.2020.09.003.
17. Kozin ED, Lee DJ, Pollak N.Getting started with endoscopic ear surgery. Otolaryngol Clin N
Am. 2021;54(1):45–57. https://doi.org/10.1016/j.otc.2020.09.009.
18. Meyerhoff WL, Roland PS.Physical examination of the ear. In: Paparella MM, Shumrick
DA, Gluckman JL, Meyerhoff WL, editors. Otolaryngology, vol. 1. 3rd ed. Philadelphia: WB
Saunders Co.; 1991. p.905–8.
19. Higgins Joyce A, Raman M, Beaumont JL, Heiman H, Adler M, Schmidt SM.A survey comparison of educational interventions for teaching pneumatic otoscopy to medical students.
BMC Med Educ. 2019;19(1):79. https://doi.org/10.1186/s12909- 019- 1507- 0.
20. Sebothoma B, Khoza-Shangase K.Undergraduate audiology students' perceived competence
and condence in conducting otoscopic examination following video otoscopic training. BMC
Med Educ. 2021;21(1):510. https://doi.org/10.1186/s12909- 021- 02924- 0.
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21. Jaisinghani VJ, Hunter LL, Li Y, Margolis RH. Quantitative analysis of tympanic membrane disease using video-otoscopy. Laryngoscope. 2000;110(10 Pt 1):1726–30. https://doi.
org/10.1097/00005537- 200010000- 00031.
22. Purnami N, Mulyaningsih EF, Ahadiah TH, Utomo B, Smith A. Correction to: Score of
Hearing Handicap Inventory for the Elderly (HHIE) compared to whisper test on presbycusis. Indian J Otolaryngol Head Neck Surg. 2022;74(Suppl. 1):523. https://doi.org/10.1007/
s12070- 020- 02345- 3.
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a systematic review. Otolaryngol Head Neck Surg. 2018;159(2):220–30. https://doi.
org/10.1177/0194599818770405.
24. Bansal M, Shah A, Gosai B, Shah P.A Novel 3-step tuning fork hearing test; preliminary
report on its clinical utility. Indian J Otolaryngol Head Neck Surg. 2022;74(2):234–41. https://
doi.org/10.1007/s12070- 022- 03095- 0.
25. Burkey JM, Lippy WH, Schuring AG, Rizer FM.Clinical utility of the 512-Hz Rinne tuning
fork test. Am J Otol. 1998;19(1):59–62.
26. Sheehy JL, Gardner G Jr, Hambley WM.Tuning fork tests in modern otology. Arch Otolaryngol.
1971;94(2):132–8. https://doi.org/10.1001/archotol.1971.00770070368009.
S. Celik et al.
Selection andApplication Principles
ofHearing Aids inPediatric andAdult
11
Population
BahtiyarCelikgun, BulentSerbetcioglu,
andMooKyunPark
11.1 Introduction
Hearing aids are electronic devices equipped with technology that supports the
peripheral auditory system (especially the outer hair cells) that has lost all or part of
its function. They collect sounds from the environment through their microphones,
convert them into electrical energy, amplify them, and transmit them to the ears of
the person by converting them back into acoustic energy through their receivers.
Because hearing is one of the most important basic senses, hearing aid technology
has evolved throughout history to connect hearing-impaired people to society. This
journey, which began with ear trumpet hearing aids and became widespread with
the development of the rst stethoscope by Rene Laennec in the eighteenth century,
continues today with advanced assistive devices supported by “articial intelligence.” [1] After the digitalization revolution in hearing aids in the mid-1990s, hearing aids went beyond simple amplication tools and entered the category of
electronic devices that recognize the human voice and contribute to the ability to
understand speech in noise. From this point on, hearing aids have the role of assisting both the central and peripheral auditory systems. Today, hearing aids which
incorporate, many psychoacoustic and assistive technologies consist of six basic
parts: microphone, amplier, receiver, battery, earmold/dome, and processor.
B. Celikgun (*) · B. Serbetcioglu
Faculty of Health Sciences, Department of Audiology, Medipol University, Istanbul, Türkiye
e-mail: mbserbetcioglu@medipol.edu.tr
M. K. Park
Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University
Hospital, Seoul, South Korea
Sensory Organ Research Institute, Seoul National University Medical Research Center,
Seoul, South Korea
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2024
M. T. Kalcioglu et al. (eds.), Otology Updates, Comprehensive ENT,
https://doi.org/10.1007/978-3-031-76173-7_11
203
204
B. Celikgun et al.
11.2 Basic Components oftheHearing Aids
Although today’s hearing aids have advanced digital sound processing capabilities
and advanced chip technologies, they still require basic hardware to provide acoustic energy conversion and amplication.
11.2.1 Microphone
Microphones are transducers that convert acoustic energy collected from the
environment over a wide frequency spectrum into electrical energy. Microphones
should not consume too much of the already limited power source (battery),
should be adaptable to hearing instrument sizes, and should have the most accurate frequency response possible. As technology has evolved, hearing instrument manufacturers have changed their microphone preferences. Since the
1960s, the microphone of choice for hearing instrument manufacturers has been
the electret condenser microphone (ECM; Fig.11.1a). These microphones are
ideal in size and have a very accurate frequency response. They work by converting the change in capacitance caused by diaphragm movement due to acoustic stimulation into electricity. However, the fact that these microphones are
affected by ambient temperature and stability problems has led manufacturers to
search for alternative microphones. This search, which has been ongoing since
the 2010s, has led manufacturers to use microelectromechanical systems
(MEMS) microphones in some hearing aid models. These microphones consist
of a exibly suspended diaphragm that moves freely over a xed back plate, all
fabricated on a silicon wafer. An incoming sound wave passing through the
holes in the back plate causes the diaphragm to move in proportion to the compression, and rarely the amplitude, of the waves. This action changes the distance between the diaphragm and the backplate, and this change in capacitance
is converted into an electrical signal. MEMS microphones, which are used in
some hearing aid models today, offer high stability and extremely low-power
consumption [2, 3].
11.2.2 Amplifier
This component amplifies the electrical energy transmitted by the microphone
with appropriate changes in current and voltage. Microphones convert acoustic energy into electrical energy and send it to an amplifier. The amplifier
provides frequency- specific amplification for hearing aids and delivers amplified sound to the receiver. While analog amplifiers were used in hearing aids
until the mid-1990s, digital amplifiers were introduced with the digitalization
revolution. Today, Class D amplification systems are used in hearing aids
(Fig.11.1b). These systems have small size, low-power consumption, and low
distortion [4].
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
205
a
bc
de
f
g
Fig. 11.1 Basic hearing aid components (a-Microphone, b-RITE amplier, c-BTE receiver,
d-RITE receiver, e-Batteries, f-BTE, and RITE earmolds, g- RITE domes)
11.2.3 Receiver
The electrical energy amplied by the amplier was converted back into acoustic energy by the receiver and transmitted to the human ear. This energy conversion is achieved by the interaction of the xed and variable magnetic systems.
The electric current owing through the coils wound on a metal plate creates a
temporary magnetic effect in the system. The electromagnetic eld interacts
with the xed magnetic eld of the magnet inside the coil, and the interaction
between these two magnetic elds creates vibrations. When a signal arrives, it
moves under the inuence of an electromagnetic force. Since the coil was xed
to the diaphragm, it also moved through the diaphragm. The movement of the
diaphragm adapts to changes in the electrical signal, and sound waves are
produced.
206
B. Celikgun et al.
The method of using ampliers in the hearing aid may depend on the hearing aid
model. Traditional behind-the-ear (BTE) hearing aids have receivers located inside
the hearing aid housing, while the most popular receiver-in-the-ear (RITE) models
have receivers located outside the hearing aid housing (Fig.11.1c and d). In addition,
the physical size of the receiver varies according to the acoustic power produced by
the hearing instrument. For example, physically smaller receivers are preferred in
small invisible-in-the-canal (IIC) hearing instruments that are placed in the ear canal,
while larger receivers are used in very powerful ultra-power (UP, super power (SP))
BTE models. This difference is not only limited to physical dimensions but also to the
acoustic characteristics they offer. For example, the frequency response and frequency-specic gain of a receiver in a standard BTE and a BTE UP can be completely
different. The data sheets provided by hearing instrument manufacturers on their websites usually also show the acoustic characteristics of the hearing instrument models.
11.2.4 Batteries
Hearing aids, like any electronic device, require electrical power. Currently, power
is provided by two types of batteries: disposable and rechargeable. The use of
rechargeable batteries in particular has become widespread in recent years with the
use of lithium-ion batteries by manufacturers. However, disposable batteries are
also often preferred by manufacturers today.
Hearing aids that use rechargeable batteries are typically charged in their carrying case, which contains an internal battery. Similar to true wireless earphones,
hearing aids in a box are charged by internal batteries in the carrying case, either
contact or contactless. These carrying cases, which are typically fully charged in
three to four hours, can charge the hearing aids 3–5 times. On the other hand, there
are desktop chargers designed for home/work use. The batteries in these devices,
which typically last one day on a single full charge, are replaced by the service
technician after the maximum charge cycle. Some new-generation carrying cases
can also be used as dehumidiers.
The characteristics of disposable batteries vary depending on the model, size,
and acoustic performance of the hearing aid. Small RITE or custom hearing aids
typically use batteries numbered 10, represented by the yellow color. RITE or some
custom models use batteries numbered 312, which are atter and represented by the
brown color. Traditional BTE models use number 13 batteries, which are thicker
than 312 and packaged in orange, while powerful BTE UP models use number 675
batteries, which are packaged in blue (Fig.11.1e).
11.2.5 Earmolds/Domes
The earmolds ensure that the hearing aids remain rmly in place on the ear and that
the sounds amplied by the hearing aids are transmitted to the human hearing system in a healthy way. It is important that the sounds amplied by the hearing aid at
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
207
the hearing thresholds of the hearing-impaired individual are delivered to the ear
without distortion. Therefore, the acoustic properties of the earmolds, such as the
frequency response of the hearing aids, should be considered. It should be noted that
any changes to the earmolds will also affect the acoustic performance of the
hearing aid.
Before the digital revolution in hearing aids in the mid-1990s, earmolds played
an important role in ne-tuning hearing aids. In today’s digital world, ne-tuning,
which can only be done with computer software at different audio input levels for
each frequency band, can be done with the limited features of analog hearing aids.
Bass, mid-range, and high-frequency gain can be partially adjusted with various
acoustic modications in the earmolds. For example, low-frequency gain can be
increased or decreased by opening a vent of the appropriate diameter on the earmold, high-frequency gain can be increased or decreased by using the Libby horn
tube, and mid-frequency acoustic gain can be increased or decreased by using various dampers/lters. Today, earmolds can still be acoustically modied. However,
with the increased use of computer-based tting software in a digitalized world and
the decreased use of traditional BTE models, acoustic modications have become
less important. However, it is important to remember that earmolds act as a bridge
between hearing aids and the human auditory system. If this bridge is not given due
importance, sound transfer may not occur at the desired quality and quantity.
Earmolds can be made of various soft or hard materials and come in a variety of
styles. Soft earmolds, which are more successful in preventing acoustic leakage, are
generally preferred for individuals with severe or profound hearing losses and in the
pediatric population, while hard earmolds, which better preserve acoustic properties, are preferred for mild to moderate hearing losses. In BTE hearing aids, earmolds that can be used with full shell, half shell, skeleton, concha, and probe models
can also be used with micro or concha models in RITE hearing aids (Fig.11.1f).
With the three-dimensional (3D) scanner and laser printer technology widely used
in earmold production, earmolds can be more comfortably designed to meet the
needs of the hearing aid user and produced with a lower error rate.
Plastic domes are a ready-to-use type of earmold used in RITE hearing aids and
are widely preferred today. Each manufacturer manufactures domes according to
their sound amplication strategies and sells them with a hearing aid. These special
earmolds, which come in a variety of styles and sizes (e.g., XS, S, M, L, and XL) to
accommodate different ear canals and the acoustic properties required during hearing aid use, are commonly used in three different types: bass dome, tulip dome, and
open dome (Fig.11.1g).
Acoustic Modifications on Earmolds
The earmold or dome used with a BTE or RITE hearing aid determines how the
amplication set by the computer software is delivered to the eardrum. In addition
to physical vibrations, sound is also affected by the physical structure of its environment. Naturally, amplied sound waves from the hearing aid receiver are transmitted to the eardrum by passing through the earmold and ear canal. Therefore, it is
expected that some changes in the physical structure of the earmold/dome will
208
Table 11.1 Effect of vent size on hearing aid gain (dB)
Vent size
Unvented -4
1mm
2mm
3.5mm
Open
dome
Closed
dome
250Hz 500Hz 750Hz 1kHz 1.5kHz 2kHz 3kHz 4kHz
−2 −1 −1
−5 −2 −1 −1
−11 −3 −1 −1
−21 −12 −6 −4
−30 −24 −16 −12 −8 −3
−10 −8 −3 −2 −2 −1
1 0 0 0 0
1 0 0 0 0
1 1 1 1 2
1 2 2 1 1
B. Celikgun et al.
5 0 0
1
−2
6kHz
0
affect the frequency distribution of hearing gain. Although acoustic modications to
the earmold and dome have become less important since the digital revolution in
hearing aids in the mid-1990s, various physical modications made to the earmold,
consciously or unconsciously, can affect the acoustic properties of hearing aids. The
most important type of acoustic modication that remains important in both BTE
and RITE earmolds, as well as in custom hearing aids, is the vent. A vent is a hole
that is opened in an earmold or custom device. However, this hole should be opened
to specic sizes using specic techniques depending on the individual’s hearing
thresholds and audiological conditions.
In addition, the material and type of earmold can also change the effect of the
vent on acoustic properties [5]. The effects of different vent diameters on acoustic
gain are shown in Table11.1) [6]. In addition, the type of earmold and vent size
change the occlusion effect experienced by the user. Occlusion and voice complaints are usually less common with large-vented earmolds; however, these complaints increase with non-vented earmolds, especially when low-frequency hearing
is normal or near normal. Minimal occlusion complaints are observed with open
dome applications [7].
Today, in addition to the vent diameter, the depth of the earmolds/custom hearing
aids placed in the ear canal is also important. If the part of the earmold that enters
the ear canal is longer than a standard earmold, approximately 2.5dB more hearing
gain is obtained in the 250, 500, and 750Hz frequency bands. If the custom earmold
is shorter than the standard earmold, 2–3dB more hearing gain is obtained in the
150–4000Hz range [8].
11.3 The Working Principles oftheHearing Aids: Digital
Signal Processing andCompression System
The history of hearing aid development shows that hearing aid technology is constantly evolving. A carbon transmitter developed by Thomas Edison for telephones
in 1870 demonstrated that electrical signals could be amplied [1]. Later, in 1920,
vacuum tubes took electrical ow control a step further. By the 1940s, hearing aids
were pocket-sized. In 1948, the Bell Acoustics Laboratory introduced the transistor,
which would allow hearing aids to shrink in size. Within a few years, Norman Krim
11 Selection and Application Principles of Hearing Aids in Pediatric and Adult…
209
developed commercial transistors [1] and hearing aid technology gained momentum with the introduction of the rst all-digital BTE hearing aid in 1996.
Today, hearing aids are no longer devices that collect environmental sounds,
amplify them to a certain level, and transmit them to the human ear. Hearing aids
have become articial intelligence (AI)-based assistive devices that incorporate
digital signal processing (DSP) strategies, operating systems, wireless connection
technologies, and powerful processors. Thanks to DSP technology, hearing aids
provide frequency-specic amplication, loudness control with a compression system, reduction of ambient noise, protection of the sound scene during amplication,
preservation of speech cues, protection of amplied sounds from wind noise or
feedback, and ensured wireless connection. It also coordinates all of these technologies to achieve a customized amplication goal.
Currently, hearing aids typically use two microphones to capture sounds within
the input dynamic range (IDR) set by the manufacturer and convert them into electrical energy for digital processing. These digitized sounds are analyzed using the
Fast Fourier Transform (FFT), which preserves the time and frequency domain and
is separated into “channels” using low-pass, band-pass, and high-pass lters. This
separation process makes it easier to process sounds. The number of channels in a
hearing aid is usually listed on the hearing aid’s technical data sheet. Currently,
many manufacturers process sounds using multiple channels in their hearing aids.
After frequency analysis of the sounds in a time unit with FFT, signal-noise analysis
can be performed according to certain physical properties of the sounds dened by
the manufacturer (for example, the number of amplitudes of the sound in a time
unit). Data from hearing aid microphones, AI, DSP, DNR, and accessories such as
remote microphones are also included in the sound processing. In order to amplify
sounds as distortion-free as possible, digital distortion reduction technologies such
as wind noise and feedback cancellers also contribute to the DSP.In addition, the
frequency transposition processes required by the frequency reduction technologies
are also performed within the DSP.Finally, the processed, cleaned, and amplied
sounds are converted back into acoustic stimuli through the receiver and delivered
to the ear.
Maintaining dynamic environmental noise under control is critical for hearing
aid users. Hearing aids must keep loud sounds at a comfortable level while amplifying soft sounds. This “adaptive braking” system in hearing aids is called the “compression system.” A detector connected to the DSP activates the compression system
when a loud sound enters the hearing aid, and the compression system determines
how much amplication to apply to the loud sound input. The process of detecting
and suppressing loud sounds by the compression system is called “attack time.”
During the attack time, the hearing aid input switches from moderate sounds (55dB
SPL) to loud sounds (90dB SPL), and the sounds are stabilized at 2dB (IEC 118–2)
or 3dB (ANSI S3.22). As loud sounds begin to fade, the compression system slowly
removes the suppression from the signal. This process is called “release time.” No
suppression is applied to the audio signal as long as the surrounding sounds remain
within the “safe” zone dened by the compression system. Hearing instrument
manufacturers can use “fast compression” by keeping the release time short and